But commanders in the tribal eastern alliance said top terrorists who they believed were among the al-Qaida forces may have escaped toward the nearby border with Pakistan. The whereabouts of bin Laden was unknown.

Heavy snow fell around the Tora Bora area in Afghanistan's eastern White Mountains, making escape more difficult for the Arab and foreign Muslim fighters trapped for days in a heavily forested canyon after fleeing al-Qaida caves.

U.S. warplanes provided close air support as alliance fighters -- with American special forces moving alongside to call in U.S. airstrikes -- advanced up the Milawa valley in an assault launched after a second deadline for the al-Qaida fighters to surrender passed at noon Thursday.

After sundown Thursday, B-52 bombers carpet-bombed the higher mountain ridges near the Pakistani border, creating spectacular orange flashes in the night. An AC-130 gunship resumed attacks for the third night in a row.

If not for the surrender talks over the past two days, "this would have been finished," Hazrat Ali, security chief for the eastern alliance, said.

In Washington, Defense Secretary Donald H. Rumsfeld said the Pentagon believes bin Laden is still in Afghanistan, though he acknowledged there were reports he had left the country.

He said the United States was getting "scraps of information" about bin Laden from Afghans, Pakistanis and others. "He is in hiding. We are asking everyone to help."

As for bin Laden's fighters, Rumsfeld said, "There's no doubt in my mind that any number of al-Qaida have gone across various borders and do intend to fight another day and we intend to find them and keep looking."

In part to convince any doubters -- particularly in the Middle East -- that bin Laden was behind the Sept. 11 terror attacks in the United States, the Pentagon on Thursday released a videotape of the al-Qaida leader explaining the planning of the suicide hijackings.

"We calculated in advance" the number of casualties from the attacks, the tape shows bin Laden telling a visiting Saudi sheik. The Pentagon said the video was found in a house in Jalalabad and bore a label saying it was taped Nov. 9, about a month into the U.S. airstrikes against Afghanistan.

In other developments:

In a hospital in the southern city of Kandahar, 13 injured Arab fighters strapped grenades and explosives to their waists and demanded only a few nurses be allowed into their rooms. They apparently feared the Afghan fighters who took over the city from the Taliban a week ago.

Britain was trying to put together a multinational force and make sure Afghanistan approves it before formally announcing, possibly Friday, that it will lead a peacekeeping effort.

In the eastern city of Jalalabad, 200 Pakistani prisoners who fought alongside the Taliban were released Wednesday and were making their way home. The release was made to mark of Islam's upcoming Eid al-Fitr feast that follows Ramadan.